1. Technical Field
The present invention relates to a projector.
2. Related Art
There have been known projectors each having a light modulating device for modulating light beams emitted from a light source according to image information to form an optical image and a projection lens for enlarging and projecting the optical image formed by the light modulating device onto a screen.
This type of projector needs to change the relative position of a plurality of lenses constituting the projection lens (to move the position of a focus lens (focal position), contributing to focus adjustment, of the plurality of lens relative to the other lenses in the direction of the optical axis) for the focus adjustment such that the optical image is formed on the screen. In addition, the projector performing this focus adjustment has been disclosed (for example, see JP-A-9-130712).
The projector disclosed in JP-A-9-130712 can perform electromotive focus adjustment (manual adjustment control) in which, when a user pushes an electromotive focus far switch or an electromotive focus near switch, a focal position is changed for the time for which the switch is pushed, and automatic focus adjustment (automatic adjustment control) in which, when the user pushes an automatic focus switch, the focal position is changed to a position where the image projected onto the screen is in an in-focus state.
In the automatic adjustment control, for example, the following method is generally used (for example, see JP-A-6-186474 or JP-A-8-292496).
First, a predetermined adjustment pattern image is projected onto the screen. Then, the adjustment pattern image is captured while the focal position is being changed, and the captured adjustment pattern image is analyzed. Subsequently, an in-focus position where the projected image is in the in-focus state is determined, and the focal position is set to the in-focus position.
However, in the above-mentioned focus adjustment, generally, a variable range where the focal position can be changed mechanically (hereinafter, referred to as a mechanical limit range) is set to be wider than a design range defined in the specifications of the projection lens, considering the margin of focus adjustment or manufacturing errors of the projection lens.
Therefore, when the mechanical limit range is set as described above, the focal position is changed within the wide range in the automatic adjustment control, so that much time is taken to perform focus adjustment.